Where would I be able to access information about my underground drain waste system? County records? My house was built circa 1950; I'm not sure that there would be any "blueprints" available for my home (MN).

My intent is to locate where there might be a toilet rough-in without having to break up any concrete, as well as the size of the underground pipe. I have a finished basement; it could be possible that my grandfather (the previous owner of my house) covered over a rough-in with vinyl tile...or it may very well be that I do not have one at all.

I have a neighbor with a home structurally similar and a few years older than mine, and he advised that he put in a basement bathroom/toilet on an existing rough-in; no concrete breakup required.